The growing demand for lithium-ion batteries has prompted significant research into enhancing the performance and stability of cathode materials. This study investigates the effects of high-energy ball milling on the properties of niobium dopped LiNi0.8Co0.1Mn0.1O2 (NMC811) cathode materials. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the synthesized materials. Electrochemical performance was assessed through galvanostatic charge-discharge tests. In an un-milled NMC811 sample with Nb doping, the average primary particle size was 207 nm. Nb doping combined with ball milling further reduced the primary particle size to 150 nm. However, the use of ball milling, in addition to the excessive cationic mixing caused by Nb doping, negatively affected the rate capability probably due to the increased Nb content in the Li layer. The initial discharge capacity of NMC811 for the un-milled and ball milled samples was 161.9 and 140.6 mAh g-1 at 0.1C, respectively. After 100 cycles at 0.5 C, the capacity retention for the un-milled and milled samples were 66.2 and 89.8%, respectively within the voltage range of 2.8-4.3 V. This improvement in capacity retention is attributed to the reduced particle size and enhanced structural stability, which together help maintain better performance over extended cycling.